Ideal medical material should be capable of being tightly bonded with tissues and applicable to complicated structure to strengthen the critical design of specific parts. However, most of existing implantable medical products are formed of one single material. To take the orthopedic products, such as bone screws, spinal fixation device, inter-body fusion device, artificial disk, and artificial joints that are implanted into bone tissues, for example, most of the orthopedic products are formed of one single material, such as a metal or a biomedical polymer material.
In respect of the applicableness of the material and the compatibility between the material and human bone tissues, although metal material has excellent strength of support and osseo-integration, stress shielding effect may still occurs at normal bone tissue interface due to the huge difference in the elastic modulus between bone tissues and metal material and cause bone tissue structure to collapse. Biomedical polymer material that is characterized as a bio-inert and hydrophobic material lacking the function of inducing bone cells to grow and attach thereon cannot be easily fused with bone cells and has the risk of pull out the bone tissues, despite having an elastic modulus similar to human bone tissues and being capable of reducing the stress shielding effect through suitable distribution of stress to avoid the collapse and loss of bone tissues. Currently, composite material composed of metal and biomedical polymer is applied to produce implant devices for osseous integration to get the benefits respectively provide by the metal material and the biomedical polymer material.
However, since the implant devices for osseous integration composed by the metal/biomedical polymer based composite material still do not have enough bonding strength for resisting the sudden impact resulted from the surgical operation or the prolonged extrusion stress provided by the peripheral cartilage or bone tissues, thus delamination of the implanted device may occur and the components of the implanted device may shift to unwanted location.
Therefore, it is necessary to provide an advanced osseous integration implant device.